[flexiglass] Hooks up real app state and logic in keyguard (3)

- Connects the unlock logic to Flexiglass to let it unlock the device.

Bug: 280883900
Test: Unit tests still pass.
Test: manually verified that unlocking the device through the Flexiglass
bouncer actually unlocks the actual device.
Test: manually verified that locking the device using the power button (with "instantly lock device" setting both
on and off) properly locks the device and moves back to the Lockscreen scene that shows the
lock icon as locked.
Test: verified that above with no lock screen, swipe method, PIN,
pattern, and password methods.

Change-Id: I1cfb71ab31cf2ddda54c8009656a58b3f64e6fa6